Unbreakable and economical optical sensor array and keyboard musical instrument using the same

ABSTRACT

An optical sensor array includes plural sensor heads arranged on a supporting plate at intervals for monitoring moving objects such as black/white keys of a composite keyboard musical instrument; the sensor head has resiliently deformable arms on both side portions thereof and a locating hole/guide groove are formed in the reverse surface portion of the sensor head, and an expander, a grip and projections are formed in the supporting plate; when a worker slides the sensor head on the expander, the resiliently deformable arms make the gap wider so that the grip is pinched between the resiliently deformable arms and that the projections are engaged with the locating hole and guide groove, whereby the sensor head is easily fixed to and located at a predetermined position on the supporting plate.

FIELD OF THE INVENTION

This invention relates to an optical sensor array and, moreparticularly, to an optical sensor array for detecting current positionsof plural moving objects such as, for example, keys and hammersincorporated in a keyboard musical instrument and a keyboard musicalinstrument using the same.

DESCRIPTION OF THE RELATED ART

Several sorts of composite keyboard musical instruments are sold in themarket. A composite keyboard musical instrument is a compromise betweenan acoustic keyboard musical instrument, i.e., a piano and an electronickeyboard. A player can selectively play a tune through acoustic soundand electronic sound. This sort of composite keyboard musical instrumenthas been known as “silent piano”. When a pianist instructs the silentpiano to enter the acoustic sound mode, a hammer stopper is moved out ofthe trajectories of hammers so as to permit the hammers selectively tostrike the strings for generating the piano tones. On the other hand, ifthe pianist wishes to practice the fingering on the keyboard, he or shechanges the silent piano to the silent mode. Then, the hammer stopper ismoved into the trajectories of the hammers. While the pianist isfingering a tune on the keyboard, the action mechanism selectivelydrives the hammers for rotation. Although the hammers escape from theaction mechanism, they rebound on the hammer stopper before striking thestrings. No string vibrates. Thus, the pianist can practice thefingering without disturbance to his or her neighbors.

The silent piano is equipped with an electronic sound generating system.The electronic sound generating system comprises an array of keysensors, an array of hammer sensors, a data processing unit and aheadphone. The array of key sensors is provided under the array of blackand white keys, and supplies key position signals representative of thecurrent key positions of the associated black and white keys to the dataprocessing unit. On the other hand, the array of hammer sensors isprovided in the vicinity of the array of the hammers, and supplieshammer position signals representative of the current hammer positionsof the associated hammers to the data processing unit. The dataprocessing unit periodically fetches the key position signals and hammerposition signals from the signal ports assigned thereto, and accumulatespieces of data information representative of the variation of key/hammerposition of each key/hammer in the data storage. The data processingunit periodically checks the data storage to see whether or not thepianist depresses any one of the black/white keys for generating a tone.If the data processing unit finds the pianist to depress a black/whitekey, the data processing unit determines the key velocity and timing atwhich the piano to is to be generated. The data processing unit producesmusic data codes representative of the tone to be produced, and convertsthe music data codes to an audio signal. The audio signal is supplied tothe headphone, and the pianist hears the electronically produced tonethrough the headphone. Thus, the key/hammer sensors are indispensablecomponent parts of the silent piano.

FIG. 1 shows a prior art optical sensor array 100. The prior art opticalsensor array serves as the key sensors, and is provided under the arrayof black/white keys. Reference numeral 101 designates shutter plates.The shutter plates are attached to the black/white keys, respectively,and downwardly project from the lower surfaces of the associatedblack/white keys.

The prior art optical sensor array 100 largely comprises a supportingplate 103, plural sensor heads 104 and pairs of optical fibers 105/111.Slits 102 are formed in the supporting plate 103 at intervals, and theshutter plates 101 are aligned with the slits 102, respectively. Theslits 102 are wider than the shutter plates 101, and permit the shutterplates 101 to be moved deeply into the space under the supporting plate103.

The plural sensor heads 104 are attached to the supporting plate 103 atintervals, and are located on both sides of the slits 102. Thus, thesensor heads 104 are arranged such that the shutter plates 101 projectinto and are retracted from the gaps between the sensor heads 104.

The sensor heads 104 are formed of transparent acrylic resin, and have aconfiguration like a combination of large and small rectangularparallelepiped blocks. The small rectangular parallelepiped blockprojects from an end surface of the large rectangular parallelepipedblock, and shoulders take place on both sides of the small rectangularparallelepiped block. A light outlet port 108 is provided on one of theshoulders, and a light inlet port 112 is provided on the other shoulder.The light outlet port 108 and light inlet port 112 of each sensor head104 are aligned with the light inlet port 112 of one of the adjacentsensor heads 104 and the light outlet port 108 of the other adjacentsensor head 104. Thus, the light outlet ports 108 and the light inletports 112 are provided on optical paths.

A prism 106 and a collimator lens 107 as a whole constitute the lightoutlet port 108, and a condenser lens 109 and a prism 110 form incombination the light inlet port 112. Two holes are formed in the largerectangular parallelepiped block, and are open to the shoulders and theother end surface. The optical fiber 105 is inserted into one of theholes, and reaches the prism 106. The other optical fiber 111 is alsoinserted into the other hole, and reaches the prism 110.

Though not shown in FIG. 1, a light emitting device (not shown) isconnected to the other end of the optical fiber 105, and a lightdetecting device is connected to the other end of the optical fiber 111.When the light emitting device is energized, light is radiated from thelight emitting device into the optical fiber 105, and optical fiber 105propagates the light to the prism 106. The light is reflected on theoblique surface of the prism 106, and is formed into a parallel raythrough the collimator lens 107. The parallel ray proceeds toward thelight inlet port 112 of the adjacent sensor head 104, and is incidentinto the light inlet port 112 of the adjacent sensor head 104.

The incident light is reflected on the oblique surface of the prism 110,and is fallen into the optical fiber 111. The optical fiber 111propagates the light to the light detecting device, and the lightdetecting device converts the light to photo current.

A pianist is assumed to depress a black/white key. The black/white keyis sunk, and, accordingly, the shutter plate 101 is moved downwardly.The shutter plate 101 reaches the optical path, and gradually interruptsthe parallel ray. Accordingly, the amount of incident light is reduced,and the light detecting device reduces the photo-current. Thus, thecurrent key position is converted to the amount of photo-current.

FIG. 2 shows another prior art optical sensor array. The prior artoptical sensor array comprises the supporting plate 103, sensor heads121/122 and optical fibers 105/111. The sensor heads 121/122 arealternated with the slits 102, and each sensor head 121/122 isassociated with only one optical fiber 105/111.

The sensor head 121/122 comprises a body 121 a and a pair of lenses107/109. The body 121 a has side surfaces parallel to each other, andthe lenses 107/109 are attached to the side surfaces. A notch forms apair of oblique surfaces 120 in the body 121 a, and the optical fiber105/111 is retained by the body 121 a in such a manner that light isradiated to and received from the pair of oblique surfaces 120.

The optical fibers 105/111 are connected to a combined optical device,i.e., the combination of light-emitting and light-detecting elements.The combined optical device sequentially supplies light to the sensorheads 121. This means that the combined optical device supplies thelight to the sensor head 121 on the right side of the sensor head 122 ina time slot and to another sensor head 121 on the left side of thesensor head 122 in another time slot. Although the sensor head 122receives the light from both sensor heads 121, the timing is differentbetween the sensor 121 head on the right side and the sensor head 121 onthe left side so that the data processing unit can determine which thelight source is.

Assuming now that the combined optical device supplies the light to thesensor head 121 on the right side of the sensor head 122, the light isradiated from the optical fiber 105 toward the oblique surfaces 120, andis reflected toward both side surfaces where the lenses 107 areattached. Thus, the light beam is split into two light beams, and isradiated through the lenses 107 toward the adjacent sensor heads. One ofthe split light beams is incident on the lens 109, and the incidentlight is reflected toward the optical fiber 111. The optical fiber 111propagates the light to the combined optical device, and the light isconverted to photo-current. The photo-current is converted to a keyposition signal, which is supplied to the data processing unit.

When the combined optical device supplies the light to the sensor head121 on the left side, the light is incident on the sensor head 122. Theright is reflected on the oblique surfaces 120, and the reflected lightis incident on the optical fiber 111. The optical fiber 111 propagatesthe light to the combined optical device, and the combined opticaldevice converts the light to photo-current. The photo-current is alsoconverted to the key position signal, which is supplied to the dataprocessing unit. The data processing unit discriminates the key positionsignal on the basis of the timing and the combination of the sensorheads 121/122.

The prior art optical sensor arrays are so compact that the manufacturercan install it in a narrow space inside the composite keyboard musicalinstrument.

In the above-described prior art optical sensor arrays, the sensor heads104 and 121/122 are arranged on the rear surfaces of the supportingplates 103. The light outlet ports 108/107 are to be exactly alignedwith the light inlet ports 112/109 of the adjacent sensor heads 104/122.For this reason, the assembling workers are expected to pay closeattention to the assemblage.

The sensor heads 104 and 121/122 are fixed to the rear surfaces of thesupporting plates 103 by means of adhesive compound. However, theadhesive compound requires a time for solidification. In order to keepthe relative position between the sensor heads 104 and 121/122 and thesupporting plates 103, the supporting plates are formed with holes, andprojections are formed in the lower surfaces of the sensor heads 104 and121/122. The holes and projections serve as a positioner, and themanufacturer gives a tight tolerance to the positioner. When anassembling worker locates the sensor head 104 or 121/122 at a targetposition on the lower surface of the supporting plate 103, he or shebrings the sensor head 104 or 121/122 over the hole, and stronglypresses it against the supporting plate 103. Then, the projection isforced into the hole. The assembling worker injects the sensor head 104and 121/122 with adhesive compound. After a short time, the adhesivecompound is solidified, and the sensor head 104 or 121/122 is fixed tothe supporting plate 103.

The first problem inherent in the prior art optical sensor arrays isthat the sensor heads 104 and 121/122 are liable to be broken in theassembling work. The sensor heads 104/121/122 measure 5-10 millimetersby 5-10 millimeters, and large force is required for inserting theprojection into the hole due to the tight tolerance. The sensor heads104/121/122 are not so strong that the small sensor heads 104/121/122can not withstand the large force.

The second problem is low productivity. The sensor heads 104/121/122 arefinally fixed to the supporting plates 103 by means of the adhesivecompound, and the adhesive compound requires a time for solidification.This means that the assembling worker has to stand idle until thesolidification of the adhesive compound. Even though the assemblingworker starts the assembling work on another one before thesolidification of the adhesive compound on the previous one, theassembling worker at the next stage still waits for the solidificationof the adhesive compound on the previous one. Thus, the assemblingworkers consume a large amount of time and labor, and the manufacturersuffers from the low productivity.

The third problem inherent in the prior art optical sensor arrays ispoor repairability. When an assembling worker fixes the sensor heads104/121/122 to the supporting plate 103, the lenses 107/109 are liableto contaminated with the adhesive compound. Even if the assemblingworker is notified immediately after injecting the adhesive compound,the assembling worker feels the separation of the contaminated sensorhead 104/121/122 from the supporting plate 103 hard, because theprojection is tightly received in the hole. If the assembling worker isnotified after the solidification of the adhesive compound, it isimpossible to separate the sensor head 104/121/122 from the supportingplate 103.

Thus, the prior art optical sensor arrays are breakable and poor inproductivity and repairability. Nevertheless, the optical sensor arraysare indispensable for the composite keyboard musical instruments. Thismeans that the prior art composite keyboard musical instruments areexpensive. Thus, the prior art composite keyboard musical instrument hasa problem in the production cost.

SUMMARY OF THE INVENTION

It is therefore an important object of the present invention to providean optical sensor array, which is unbreakable, high in productivity andrepairability.

It is also an important object of the present invention to provide akeyboard musical instrument, the production cost of which is improved byusing the optical sensor array.

To accomplish the object, the present invention proposes to connectsensor heads to and located them at target positions on retainingportions through sliding motion of the sensor heads on the retainingportions.

In accordance with one aspect of the present inventor, there is providedan optical sensor array for converting current positions of movingobjects to signals comprising a supporting plate having plural retainingportions at intervals, plural sensor heads respectively assigned to theplural retaining portions and establishing optical paths for light beamsacross the intervals, a combined optical device optically connected tothe plural sensor heads and selectively supplying light to and receivingthe light from the plural sensor heads through the optical paths, plurallight modifiers connected to the moving objects and moved in the opticalpaths for modifying the light beams depending upon the current positionsof the associated moving objects, and plural locating connectors formedpartially in the plural sensor heads and partially in the pluralretaining portions and connecting the plural sensor heads to targetpositions on the retaining portions through sliding motion of the sensorheads on the associated retaining portions.

In accordance with another aspect of the present invention, there isprovided a keyboard musical instrument for generating audible tones froman electric signal comprising plural tone specifying mechanismsselectively actuated by a player for specifying tones to be generated, atone generating unit generating the tones specified by the playerthrough the plural tone specifying mechanisms, and an optical sensorarray monitoring the plural tone specifying mechanisms so as todetermine the tone specifying mechanisms actuated by the player andincluding a supporting plate having plural retaining portions atintervals, plural sensor heads respectively assigned to the pluralretaining portions and establishing optical paths for light beams acrossthe intervals, a combined optical device optically connected to theplural sensor heads and selectively to supplying light to and receivingthe light from the plural sensor heads through the optical paths, plurallight modifiers connected to the plural tone specifying mechanisms andmoved in the optical paths for modifying the light beams depending uponthe current positions of the associated tone specifying mechanisms andplural locating connectors formed partially in the plural sensor headsand partially in the plural retaining portions and connecting the pluralsensor heads to target positions on the retaining portions throughsliding motion of the sensor heads on the associated retaining portions.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the optical sensor array will be moreclearly understood from the following description taken in conjunctionwith the accompanying drawings, in which

FIG. 1 is a bottom view showing the arrangement of the prior art opticalsensor array,

FIG. 2 is a bottom view showing the arrangement of another prior artoptical sensor array,

FIG. 3 is a side view showing the internal structure of a silent pianoaccording to the present invention,

FIG. 4 is a perspective view showing the arrangement of an opticalsensor array incorporated in the silent piano,

FIG. 5 is a cross sectional view taken along line A-A′ and showing therelative position between a hammer and one of the optical sensors,

FIG. 6 is a plane view showing the arrangement of sensor heads,

FIG. 7 is a plane view showing the sensor head in detail,

FIG. 8 is a cross sectional view taken along line B—B of FIG. 10 andshowing the configuration of the guide hole,

FIG. 9 is a cross sectional view showing a part of the guide holeencircled in broken line C of FIG. 8,

FIG. 10 is a rear view showing resiliently deformable arms formed in thesensor head,

FIG. 11 is a bottom view showing parts of a locating connector formed inthe sensor head,

FIG. 12 is a plane view showing the configuration of a supporting plate,

FIG. 13 is a plane view showing an assembling work on the optical sensorarray,

FIG. 14 is a diagram showing the connections between the sensor headsand a combined optical device,

FIG. 15 is a diagram showing the relation between black/white keys andthe sensor heads in the silent piano,

FIG. 16 is a plane view showing the first modification of the supportingplate,

FIG. 17 is a plane view showing the second modification of thesupporting plate,

FIG. 18 is a plane view showing the third modification of the supportingplate,

FIG. 19 is a plane view showing the fourth modification of thesupporting plate,

FIG. 20 is a plane view showing a modification of the sensor head, and

FIG. 21 is a side view showing a shutter plate with which the sectorialplate is replaced.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 3 of the drawings, a silent piano embodying thepresent invention largely comprises an acoustic piano 1, a hammerstopper 2 and an electronic sound generating system 3. In this instance,the acoustic piano 1 is a grand piano, and comprises a keyboard, actionunits 4, hammers 5, damper units 6 and strings 7. The keyboard is placedon a key bed, which forms a part of the piano case, and includes pluralblack keys 8 a and white keys 8 b. The black keys 8 a and white keys 8 bare laid on the well-known pattern, and are rotatably supported by abalance rail 8 c. In this instance, eighty-eight black/white keys 8 a/8b are incorporated in the keyboard.

A center rail 4 a laterally extending over the rear portions of thekeyboard. The action units 4 are rotatably supported by the center rail4 a, and are held in contact with balance pins 8 d projecting from theassociated black/white keys 8 a/8 b. Thus, the black/white keys 8 a/8 bare linked with the associated action units 4, and give rise to rotationaround the center rail 4 a when a pianist depresses the black/white keys8 a/8 b.

Action brackets 8 e are provided on the key bed at intervals, and arelaterally spaced from one another. A shank flange rail 5 a laterallyextends over the keyboard, and is supported by the action brackets 8 e.The hammers 5 have hammer shanks 5 b and hammer heads 5 c. The hammerheads 5 c are connected to the hammer shanks 5 b, respectively. Thehammer shanks 5 b are swingably connected to the hammer shank rail 5 a,and are rest on the associated action units 4. Thus, the hammers 5 arelinked with the associated shank flange rail 5 a, and are driven forrotation by the associated action units 4.

A damper lever rail 6 a laterally extends at the back of the keyboard,and the damper units 6 have damper levers 6 b and damper heads 6 c. Thedamper levers 6 b are swingably supported by the damper lever rail 6 a,and projects into the space over the rear end portions of theblack/white keys 8 a/8 b. The damper heads 6 c are respectivelyconnected to the damper levers 6 b, and are rest on the associatedstrings 7. The strings 7 are stretched over the array of hammers 5, andare to be struck with the associated hammers 5.

The hammer stopper 2 laterally extends over the hammers 5, and ischanged between a free position and a blocking position by means of asuitable actuator such as, for example, a link mechanism or an electricmotor. When the player changes the hammer stopper 2 to the blockingposition, the hammer stopper 2 directs the shock absorber 2 a toward thehammer shanks 5 b, and the shock absorber 2 a enters the trajectories ofthe hammer shanks 5 b. On the other hand, when the pianist changes thehammer stopper 2 to the free position, the hammer stopper 2 rearwarddirects the shock absorber 2 a, and the shock absorber 2 a is evacuatedfrom the trajectories of the hammer shanks 5 b.

The player is assumed to depress the white key 8 b. The front portion ofthe white key 8 b is sunk toward an end position, and gives rise to therotation of the associated action unit 4 about the center rail 4 a inthe counter clockwise direction. Accordingly, the hammer 5 is graduallyrotated about the shank flange rail 8 f in the clockwise direction. Therear end portion of the white key 8 b is brought into contact with thedamper lever 6 b, and gives rise to rotation of the damper lever 6 babout the damper lever rail 6 a.

The player further exerts the force on the white key 8 b. The rear endportion of the white key 8 b lifts the damper head 6 c, and makes thedamper head 6 c spaced from the associated string 7. The action unit 4escapes from the hammer 5 on the way to the end portion. Then, thehammer 6 starts the free rotation about the shank flange rail 8 f. Thehammer is getting closer and closer to the associated string 7.

If the player keeps the hammer stopper 2 at the free position, the shockabsorber 2 a is out of the trajectories of the hammer shanks 5 b, andthe string 7 is struck with the hammer head 6 c. The string 7 vibrates,and generates the piano tone. On the other hand, if the player haschanged the hammer stopper 2 to the blocking position, the shockabsorber 2 a is in the trajectories of the hammer shanks 5 b. The hammershank 5 b rebounds on the shock absorber 2 a before the hammer head 5 creaches the string 7 so that any piano tone is not generated.

Upon rebounding on either string or hammer stopper, the hammer 5 returnstoward the rest position. A back check 8 f, which is upright on the rearend portion of the key, receives the hammer 5. When the player releasesthe white key 8 b, the damper 6 is brought into contact with the string7, again, and, thereafter, the white key 8 b and the action unit 4return to the respective rest positions.

The electronic sound generating system 3 includes an array of keysensors 9 a, an array of hammer sensors 9 b, a data processing unit 9 cand a headphone 9 d. One of or each of the sensor arrays 9 a/9 b isimplemented by an optical sensor array 10 embodying the presentinvention. If the optical sensor array 10 serves as one of the sensorarrays 9 a/9 b, another sort of optical sensor array is available forthe other of the sensor arrays 9 a/9 b. The array of key sensors 9 a isconnected to a signal input port of the data processing unit 9 c, andthe array of hammer sensors 9 b is connected to another signal inputport of the data processing unit 9 c.

The array of key sensors 9 a is provided under the black/white keys 8a/8 b, and monitors the black/white keys 8 a/8 b for reporting currentkey positions to the data processing unit 9 c. On the other hand, thearray of hammer sensors 9 b is provided in the vicinity of the hammershanks 5 b, and is supported by the shank flange rail 5 a. The keysensors and hammer sensors are accommodated in suitable photo-shieldedcases, and are not seen in FIG. 3.

The data processing unit 9 c periodically fetches pieces of positionaldata information representative of current key positions and currenthammer positions, and accumulates the pieces of current key/hammerpositions in a data memory thereof. The data processing unit 9 c checksthe data memory to see whether or not any one of the keys/hammers 8 a/8b/5 changes the current position after the previous data fetch. If theanswer is given negative, the data processing unit 9 c repeats theperiodical data fetch and analysis. When the data processing unit 9 cfinds that the player depresses a black/white key 8 a/8 b, the dataprocessing unit 9 c specifies the depressed key, and predicts a time atwhich the hammer head 5 will strike the string 7. The data processingunit 9 c waits for the hammer position signal representative of thevariation of the current hammer position of the associated hammer 5.When the hammer 5 reaches a detectable range of the hammer sensor 9 b,the hammer sensor 9 b varies the hammer position, and the dataprocessing unit 9 c calculates the hammer velocity on the basis of theseries of current hammer position. The data processing unit 9 cdetermines the loudness of an electric tone proportionally to the hammervelocity.

The data processing unit 9 c waits for the time at which the hammerstrikes the string 7. When the time comes, the data processing unit 9 cproduces music data codes representative of the depressed key 8 a/8 b,note-on, loudness of electric tone and so forth, and a tone generator,which is incorporated in the data processing unit 9 c, produces an audiosignal from the music data codes. The audio signal is supplied to theheadphone 9 d, and is converted to the electronic tone.

When the player releases the depressed key 8 a/8 b, the black/white key8 a/8 b starts to return toward the rest position. The associated keysensor notifies the data processing unit 9 c of the backward motion. Thedata processing unit 9 c produces music data codes representative of thereleased key 8 b and note-off, and supplies them to the tone generatorat the time when the damper head 6 c is brought into contact with thestring 7. The tone generator decays the audio signal. Then, theelectronic tone is decayed.

While the player is fingering on the keyboard, the data processing unit9 c cooperates with the sensor arrays 9 a/9 b, and repeats theabove-described data processing sequence for each depressed/releasedkey. As a result, the silent piano generates electronic tones instead ofthe piano tones so that the player can confirm his or her fingeringthrough the headphone 9 d.

Description is hereinbelow made on an optical sensor array 10 withreference to FIGS. 4, 5 and 6 of the drawings. The optical sensor array10 is available for the array of key sensors 9 a and/or the array ofhammer sensors 9 b. Nevertheless, the optical sensor array 10 shown inFIGS. 4 to 6 is used as the array of hammer sensors 9 b in thisinstance.

The optical sensor array 10 comprises sectorial plates 13, a supportingplate 20 a, a cover plate 20 b, plural sensor heads 22, optical fibers25 a and a combined optical device 25 b. The sectorial plates 13 arefixed to the joint end portions of the hammer shanks 5 b, respectively,and a gray scale is printed on the sectorial plates 13. Although thegray scale is printed, the sectorial plates 13 permit light to passtherethrough.

The supporting plate 20 a laterally extends over the hammer shanks 5 b,and is fixed to the shank flange rail 5 a by means of bolts. Pluralslits 21 are formed in the supporting plate 20 a, and are laterallyspaced at intervals equal to the pitches of the array of hammers 5. Thesectorial plates 13 are respectively assigned to the slits 21, and arepartially in the slits 21. While the hammers 5 are rotating toward theassociated strings 7, the sectorial plates 13 further project into theslits. Thus, the sectorial plates 13 are movable with respect to theshank flange rail 5 a.

The sensor heads 22 are arranged on the supporting plate 20 a at theintervals, and are alternated with the slits 21. The sensor heads 22 arefixed to the supporting plate 20 a, and are stationary with respect tothe shank flange rail 5 a. Plural light emitting elements and plurallight-detecting elements constitute the combined optical device 25 b.The combined optical device 25 b is connected through the optical fibers25 a to the sensor heads 22 so that light is radiated from selected ones22A of the sensor heads 22 through the associated sectorial plates 13 tothe adjacent sensor heads 22B. The sensor heads 22A and 22B form pluralcombinations equal to the hammers 5. While the hammer 5 is rotating, theassociated plate 13 gradually changes the relative position between thegray scale and the associated sensor head, and the current hammerposition is converted to the amount of light incident onto the adjacentsensor heads 22.

The supporting plate 20 a is assembled with the cover plate 20 b so asto form the photo-shielded case. The sensor heads 22 are photo-shieldedby virtue of the photo-shielded case, and is less influenced with theenvironmental light. The component parts of the optical sensor array 10are hereinbelow described in detail.

Sensor Head

The sensor heads 22 are formed of transparent synthetic resin such as,for example, acrylic resin. The synthetic resin has a value ofrefractive index equal to or close to that of the optical fiber. Thesensor heads 22 is monolithic, and has a cross-like configuration. Thesensor head 22 is divided into three portions, which are hereinbelowreferred to as a narrow portion 22 a, a wide portion 22 b and a headportion 22 c.

A notch 23 is formed in the head portion 22 c so that the head portion22 c has a pair of ports 23 a/23 b. The two ports 23 a/23 b haverespective side surfaces substantially parallel to each other andrespective oblique surfaces inclined to the associated side surfaces at45 degrees. The sensor head 22 has a symmetrical line 30 (see FIG. 7),and the oblique surfaces are crossed on the symmetrical line 30. Twooblique surfaces define the notch 23, and are spaced at 90 degrees.Lenses 24 are fixed to the side surfaces. The lenses 24 serve ascollimator lenses in the sensor head 22 a and as condenser lenses in thesensor head 22B.

The central portion 22 b is formed with a rectangular pit 32 adjacent tothe head portion 22 c, and a coupling recess 31 (see FIG. 7) is formedon the inner wall partially defining the pit 32. A guide hole 26 isformed in the narrow/wide portions 22 a/22 b, and extends along thesymmetrical line. The guide hole 26 has an entrance 27 at the rear endsurface of the narrow portion 21 a, and is open to the pit 32 at theother end thereof (see FIG. 8). The optical fiber 25 a is inserted fromthe entrance 27. The optical fiber 25 a passes through the guide hole26, and enters into the rectangular pit 32.

The guide hole 26 has an inverted bell portion α, and a straight portionβ, and the pit 32 serves as a correcting portion γ. The centerlines ofthe inverted bell/straight portions α/β are substantially coincidentwith the symmetrical line 30. The inverted bell portion α is defined bya curved surface 28 so that the inverted bell portion α has the crosssection gradually reduced from the entrance 27 toward the straightportion β. The entrance 27 is wide enough to receive the optical fiber25 a. An assembling worker can easily insert the optical fiber 25 athrough the entrance 27 into the inverted bell portion α. After theinsertion, the assembling worker pushes the optical fiber 25 a into theinverted bell portion α. Then, the curved surface 28 guides the opticalfiber 25 a to the straight portion β. The inverted bell portion α islong so that the optical fiber 25 a smoothly reaches the boundarybetween the inverted bell portion α and the straight portion β withoutbending. In detail, the long inverted bell portion α is permitted tohave the gently curved surface 28, and the cross section is surelyreduced in the vicinity of the boundary. Even if the leading end of theoptical fiber 25 a is caught on the curved surface 28 near the boundary,the reduced cross section does not permit the optical fiber widely to bewarped in the inverted bell portion. If the inverted bell portion α istoo short, the cross section is to be rapidly reduced near the boundary.This means that the cross section is still wide near the boundary. Ifthe leading end of the optical fiber 25 a is caught on the curvedsurface 28 near the boundary, the optical fiber 25 a is widely warped inthe inverted bell portion α, and the optical fiber 25 a does not proceedto the straight portion β. Thus, the long inverted bell portion αprevents the optical fiber 25 a from the warp, and keeps the opticalfiber straight in the sensor head 22. If the optical fiber remainsseriously warped in the guide hole 26, the optical fiber exhibitsoptical characteristics out of the design specification, and makes thedata processing unit mistakenly determine the current hammer position.The present inventors investigated the minimum radius of curvature to beallowed. The present inventors found that the minimum radius ofcurvature was 5 millimeters. Even if the optical fibers 25 a were warpedto have the radius of curvature equal to or greater than 5 millimeters,the optical fibers 25 a could exactly relay the pieces of positionalinformation to the data processing unit. However, if the radius ofcurvature was less than 5 millimeters, the data processing unit 9 cfailed to determine the timing at which the hammers 5 passed certainpoints. Thus, the long inverted bell portion α is preferable for theoptical fibers 25 a.

The inverted bell portion α is connected to the straight portion β. Thestraight portion β has the inner diameter nearly equal to the outerdiameter of the optical fiber 25 a. The straight portion β permits theassembling worker smoothly to slide on the inner surface of the straightportion β. The straight portion β is open to the pit 32. The straightportion β is fairly long so as to force the optical fiber 25 a toproject into the pit 32 along the symmetrical line 30. Even if theoptical fiber 25 a is bent, the optical fiber 25 a straightly projectsinto the pit 32. Thus, the pit 32 serves as the correcting portion γ.The pit 32 has the width greater than the inner diameter of the straightportion β, and permits the leading end of the optical fiber 25 a toproceed to the coupling recess 31. The coupling recess 31 has acenterline aligned with the symmetrical line 30, and a tapered surfacedefines the coupling recess 31. This means that the cross section isgradually reduced from the entrance toward the bottom. The entrance iswider in cross section than the optical fiber, and the cross section isnarrower than that of the optical fiber 25 a at the bottom.

The leading end of the optical fiber 25 a proceeds through the pit 32 tothe coupling recess 31, and is inserted thereinto. The assembling workerfurther pushes the optical fiber 25 a into the guide hole 26. Then, theleading end of the optical fiber 25 a is snugly received in the couplingrecess 31 as shown in FIG. 9. Thus, the guide hole 26 and couplingrecess 31 automatically align the optical fiber 25 a with the crossingline between the oblique surfaces, and keep the optical fiber 25 a onthe symmetrical line 30. After the coupling between the optical fiber 25a and the sensor head 22, the rectangular pit 32 is filled with a pieceof adhesive compound so that the optical fiber 25 a is fixed onto thesymmetrical line.

When the light emitting element is energized, the light is propagatedthrough the optical fiber 25 a, and is radiated from the end of theoptical fiber 25 a. The light proceeds through the head portion 22 c tothe oblique surfaces, and the split light beams are reflected on theoblique surfaces toward the collimator lens 24. Since the optical fiber25 a is maintained on the symmetrical line 30, the amount of split lightbeam is equal to the amount of the other split light beam. The light isoutput from the collimator lenses 24 as parallel rays. The parallel raysare incident on the condenser lenses 24 of the adjacent sensor heads22B. The incident rays are reflected on the oblique surfaces, and arefallen onto the ends of the optical fibers 25 a. The optical fibers 25 apropagate the light to the light detecting elements of the combinedoptical device 25 b, and the light detecting elements convert the lightto photo-current.

Connectors Between Sensor Heads and Supporting Plate

The sensor heads 22 are connected to the supporting plate 20 and exactlylocated at proper positions on the supporting plates by means oflocating connectors, i.e., devices which connect the sensor heads 22 tothe supporting plate 20 at the proper positions without adjusting workby an assembling worker. The locating connectors are partially formed inthe sensor heads 22 and partially in the supporting plate 20.

FIGS. 10 and 11 illustrate the parts of the locating connector formed inthe sensor heads 22. The parts are a pair of resiliently deformable arms33, a locating hole 34 and a guide groove 35. The resiliently deformablearms 33 are integral with the wide portion 22 b, and downwardly projectfrom both sides of the wide portion 22 b. The resiliently deformablearms 33 are formed with pawls 33 a at the lower ends thereof, and arerounded at the boundary between the wide portion 20 b and the narrowportion 20 a. The pawls 33 a inwardly project from the lower ends of theresiliently deformable arms 33. The gap between the pawls 33 a isnarrower than the gap between the resiliently deformable arms 33.

The locating hole 34 is formed in the wide portion 22 b, and is open onthe reverse surface of the sensor head 22. The locating hole 34 has acenter point, which is on the symmetrical line 30. The locating hole 34is formed at a certain point that causes the lenses 24 are opposed tothe lenses of the adjacent sensor heads 22.

The guide groove 35 is formed in the narrow/wide portions 22 a/22 b, andhas a centerline coincident with the symmetrical line 30. The guidegroove 35 has a width equal to the radius of curvature of the locatinghole 34, and is merged with the locating hole 34 such that the remainingportion of the locating hole 34 is more than 180 degrees. Thus, a pairof tips χ takes place at the boundary between the locating hole 34 andthe guide groove 35. The tips χ are resiliently deformable so as topermit something to enter the locating hole 34. The inner surface, whichdefines the guide groove 35 and the locating hole 34, slopes from thereverse surface toward the ceiling.

FIG. 12 illustrates the supporting plate 20. The supporting plate 20 hasa frame portion 20 a and retaining portions 20 b, and is formed withpairs of projections 41/42. The retaining portions 20 b are spaced fromone another by the slits 21, and are connected to the frame portion 20a. The retaining portions 20 b are respectively assigned to the sensorheads 22. The pairs of projections 41/42 locate the sensor heads 22 atthe proper positions together with the locating holes 34 and the guidegrooves 35, and the sensor heads 22 are coupled to the supporting plate20 by means of the retaining portions 20 b and the arms/pawls 33/33 a.The retaining portions 20 b and the pairs of projections 41/42 serve asthe parts of the locating connector formed in the supporting plate 20.

The retaining portion 20 b has a symmetrical line 30 a, and is dividedinto a coupling sub-portion AR1 and a guide sub-portion AR2. The guidesubportion AR2 has a width narrower than the gap between the pawls 33 aso that an assembling worker brings the reverse surface of the sensorheads 22 into contact with the upper surfaces 40 a of the guidesub-portions AR2 without any interference with the pawls 33 a. Thesensor heads 22 are slidable on the upper surfaces 40 a of the guidesub-portions AR2.

The coupling sub-portion AR1 is formed with an expander 40 b, and has agrip 40 c. The grip 40 c has a width equal to the gap between the arms33, and the expander 40 b is gradually increased in width from the guidesub-portion 20 a toward the grip 40 c, and the maximum width of theexpander 40 b is greater than the width of the grip 40 c. A pair ofnotches 43 is formed at the boundary between the expander 40 b and thegrip 40 c. An assembling worker is assumed to force the sensor head 22to slide on the upper surface 40 a toward the coupling sub-portion AR1.The arms 33 are brought into contact with the expander 40 b. Theassembling worker exerts large force on the sensor head 22 in thesliding direction. The expander 40 b makes the gap between the arms 33wide, and permits the sensor head 22 to pass through the expander 40 b.Thus, the arms 33 are resiliently deformed by the expander 40 b so thatthe sensor head 22 reaches the grip 40 c. Then, the arms 33 resilientlyreturn to the initial positions. The grip 40 c is pinched between thearms 33, and the pawls 33 a press the grip 40 c to the reverse surfaceof the sensor head 22. The arms 33 are formed with projections, and theprojections are engaged with the notches 43. As a result, the sensorhead 22 is fixed to the associated retaining portion 20 b without anyadhesive compound.

The pair of projections 41/42 is to be engaged with the locating hole 34and the guide groove 35 so as to locate the sensor head 22 at the properposition on the supporting plate 20. The projections 41/42 have centerson the symmetrical line 30 a. The projections 41/42 have afrusto-conical configuration. The bottom surfaces of the projections41/42 have the diameter approximately equal to the width of the openingof the guide groove 35 and the diameter of the opening of the locatinghole 34. On the other hand, the top surfaces of the projections 41/42have the diameter approximately equal to the width of the ceiling of theguide groove 35 and the diameter of the ceiling of the locating hole 34.Thus, the projections 41/42 have a cross section corresponding to thecross section of the guide groove 35 and the cross section of thelocating hole 34.

The projection 41 is formed at a certain position that makes the lenses24 of the associated sensor head 22 opposed to the lenses 24 of theadjacent sensor heads 22 across the slits 21 when the projection 41 issnugly received in the locating hole 34. The other projection 42 isspaced from the projection 41 by a distance not longer than the distancebetween the center of the locating hole 34 and the entrance of the guidegroove 35. Even though the projection 41 can not prohibit the sensorhead 22 from rotation therearound, the projection 42 received in theguide groove 35 does not permit the sensor head 22 to rotate. Thus, theprojections 41/42, locating hole 34 and guide groove 35 locate thesensor head 22 at the proper position on the supporting plate 20.

When a worker assembles the sensor heads 22 with the supporting plate20, the worker puts the sensor head 22C on the guide sub-portion 20 b asshown in FIG. 13. The gap between the pawls 33 a is wider than the widthof the guide sub-portion 20 b so that the reverse surface of the sensorhead 22C is brought into contact with the upper surface 40 a of theguide sub-portion 20 b.

The worker slides the sensor head 22C on the upper surface 40 a in thedirection indicated by arrow AR1, and the sensor head 22C reaches theexpander 40 b. The worker presses the sensor head 22C against theexpander 40 b. Then, the arms 30 are resiliently deformed so as toincrease the gap therebetween, and permit the sensor head 22C to slideon the expander 40 b. The guide groove 35 receives the projection 41,and the sensor head 22C slides on the top surface of the projection 41.The tips χ are brought into contact with the projection 41, and theother projection 42 reaches the entrance of the guide groove 35. Theworker feels the tips χ resistive against the sliding motion. The workerincreases the force exerted on the sensor head 22. Then, the tips χ areresiliently deformed so that the projection 41 enters the locating hole34. Concurrently, the arms 33 are disengaged from the expander 40 b, andpinch the grip 40 c therebetween. The pawls 33 a press the grip 40 cagainst the reverse surface of the sensor head 22D. The locating hole 34does not permit the worker to slide the sensor head 22D in the directionindicated by the arrow AR1, and the other projection 42 does not allowthe sensor head 22D to rotate around the projection 41. Thus, the sensorhead 22D is located at the proper position where the lenses 24 areopposed to the lenses 24 of the adjacent sensor heads 22 across thetrajectories of the sectorial plates 13.

As will be understood from the foregoing description, the locatingconnectors according to the present invention makes the assemblingworker fix the sensor heads 22 to the supporting plate 20 at the properpositions without any adhesive compound. The lenses 24 are nevercontaminated with adhesive compound, and the assembling work is simplerthan that for the prior art sensor heads. This results in enhancement ofproductivity of the optical sensor array 10. The sensor heads 22 areless liable to be broken in the assembling work, because the assemblingworker only exerts the small force on the sensor heads 22 for increasingthe gap between the arms 33. Even if the sensor head 22 is broken in theassembling work, the worker is required for laterally expanding the arms33 with a suitable tool. Then, the sensor head 22 can pass the expander40 b, and reaches the guide sub-portion 20 b, again. Thus, the locatingconnector according to the present invention enhances the productivityand repairability of the optical sensor array 10. Using the opticalsensor array 10 according to the present invention, the manufacturerreduces the production cost of the silent piano.

In the above-described embodiment, the black/white key 8 a/8 b, actionunit 4 and hammer 5 as a whole constitute a tone specifying mechanism,and plural tone specifying mechanisms are incorporated in the silentpiano, and the data processing unit 9 c and headphone 9 d form incombination a tone generating unit. The arms 33, pawls 33 a, expander 40b and grip 40 c serves as a coupler between the sensor head 22 and thesupporting plate 20, and the guide groove 35, locating hole 34 andprojections 41/42 serve as a locator. The coupler and locator as a wholeconstitute the locating connector. Although the locating connector isimaginary divided into the locator and coupler, the coupler is linkedwith the locator, and each of the sensor heads 22 is connected to andlocated at the proper positions on the supporting plate 20 through acontinuous motion of the sensor head 22. In this instance, the couplerand locator are arranged in symmetry with respect to the centerlines30/30 a. The assembling worker is expected to roughly align thecenterline 30 with the centerline 30 a and, thereafter, slide the sensorhead 22 on the upper surface 40 a. Thus, the locating connectoraccording to the present invention makes the assembling work easy. Thesectorial plates 13 formed with the gray scales serve as plural lightmodifiers.

Control Sequence on Combined Photo Device

The optical sensor array 10 according to the present invention iscontrolled as follows. The moving objects, i.e., the black/white keys 8a/8 b are eighty-eight, and, accordingly, eighty-eight hammers 5 areincorporated in the silent piano. This means that the optical sensorarray 10 is expected individually to monitor the eighty-eight movingobjects 5. For this reason, eighty-nine sensor heads 22 are arranged onthe supporting plate 20. The forty-five sensor heads 22A are alteredwith the forty-four sensor heads 22B, and each hammer 5 is assigned tothe gap between the sensor head 22A and the associated sensor head 22Bas shown in FIG. 14. The eighty-nine sensor heads 22 are respectivelylabeled with numerals “1”, “2”, . . . , “5”, . . . “24”, “25”, “26”,“27”, . . . so that each sensor head is individualized with the numeral.

The combined optical device includes twelve light emitting elements suchas, for example, light-emitting diodes, i.e., LEDs 50, eight lightdetecting elements such as, for example, photo-transistors, i.e., PTRs60, a driver circuit (not shown) for selectively energizing the twelvelight-emitting diodes 50 and a current-to-voltage converter (not shown)for producing the hammer position signals from photo-current. The lightemitting diodes 50 are respectively labeled with “a”, “b2”, “c” . . .and “1”, and the photo-transistors 60 are individualized with numerals“1”, “2”, . . . , “7” and “8”. The twelve light-emitting diodes 50 areselectively connected to the sensor heads 22A through the optical fibers25 a. In this instance, each of the light-emitting diodes “a” to “m” areconnected to four sensor heads 22A, and the remaining light-emittingdiode “1” is connected to three sensor heads 22A. The four or threesensor heads 22A associated with each light-emitting diode 50 arerespectively assigned to the hammers 5 spaced at intervals of 2 octaves.The sensor heads 22B are selectively connected to the eightphoto-transistors 60 through the optical fibers 25 a. Each of the firstto seventh photo-transistors “1” to “7” is connected to six sensor heads22B, and the eighth photo-transistor “8” is connected to four sensorheads 22B. The six or four sensor heads connected to eachphoto-transistor 60 are spaced at intervals of four. For example, thephoto-transistor “1” is connected to the sensor heads “2”, “6”, “10”,“14”, “18” and “22” (see FIG. 15).

The light-emitting diodes 50 and photo-transistors 60 are assigned tothe sensor heads 22A and 22B in such a manner that each of the sensorheads 22B receives the light from only one sensor head 22A on eitherside thereof. This means that the sensor heads 22A on both sides of eachsensor head 22B do not concurrently radiate the light to the sensor head22B. The twelve light-emitting diodes 50 are respectively assigned totime slots, and twelve time slots form a single scanning cycle.

The data processing unit 9 c periodically instructs the driver circuitsequentially to energize the twelve light-emitting diodes 50 in therespective time slots. The light is propagated through the associatedoptical fibers 25 a to the sensor heads 22A, and the four or threesensor heads 22A concurrently radiate the light beams to the adjacentsensor heads 22B. The light beams are incident on the adjacent eight orsix sensor heads 22B, and the incident light is propagated through theoptical fibers 25 a to the photo-transistors. The photo-transistors 60converts the light to photo-current, and the amount of photo-current isproportional to the amount of incident light. The photo-transistors 60are respectively connected to the current-to-voltage converters so thatthe hammer position signals are produced from the photo-current.

The driver circuit is assumed to energize the light-emitting diode “a”in a certain time slot, and the light-emitting diode “a” radiates thelight. The light is distributed to the sensor heads “1”, “25”, “49” and“73”. The light beams are radiated from the sensor head “1” to thesensor head “2”, from the sensor head “25” to the sensor heads “24” and“26”, from the sensor head “49” to the sensor heads “48” and “50” andfrom the sensor head “73” to the sensor heads “72” and “74”. Thesectorial plates 13 are provided on the seven optical paths so that thelight beams are individually modulated by the gray scales on thesectorial plates 13 The sensor heads “2”, “24”, “26”, “48”, “50”, “72”and “74” are respectively connected through the optical fibers 25 a tothe photo-transistors “1” to “7” so that the combined optical device 25b concurrently supplies the seven hammer position signals to the dataprocessing unit 9 c. The data processing unit 9 c discriminates theseven hammer positions from the other hammer positions, because onlyseven light beams are valid in the tile slot.

Subsequently, the driver circuit energizes the light-emitting diode “b”in the next time slot. The light-emitting diode “b” radiates the light.The light is distributed to the sensor heads “3”, “27”, “51” and “75”.The light beams are radiated from the sensor head “3” to the sensorheads “2” and “4”, from the sensor head “27” to the sensor heads “26”and “28”, from the sensor head “51” to the sensor heads “50” and “52”and from the sensor head “75” to the sensor heads “74” and “76”. Thesectorial plates 13 are provided on the eight optical paths so that thelight beams are individually modulated by the gray scales on thesectorial plates 13. The sensor heads “2”, “4”, “26”, “28” “40”, “52”,“72”, “74” and “76” are respectively connected through the opticalfibers 25 a to the photo-transistors “1” to “8” so that the combinedoptical device 25 b concurrently supplies the eight hammer positionsignals to the data processing unit 9 c. Although the sensor heads suchas “2” and “26” received the light in the previous tile slot, the dataprocessing unit 9 c discriminates the hammers 5 represented by thehammer position signals at the sensor heads “2”, “26”, . . . from thehammers 5 represented by the hammer position signals at the same sensorheads “2”, “26”, . . . on the basis of the time slots. The dataprocessing unit 9 c compares the value of each hammer position signalswith plural thresholds so as to determine the current hammer position.The data processing unit 9 c accumulates the variation of the hammerposition in the memory, and calculates the hammer velocity on the basisof the lapse of time between the plural thresholds. Otherwise, the dataprocessing unit 9 c determines the hammer velocity on the basis of thegradient of the variation of the photo-current.

As will be appreciated from the foregoing description, the locatingconnector according to the present invention permits an assemblingworker to exactly locate the sensor heads 22 at and connect it to theproper positions on the supporting plate 20 through the continuoussliding motion. Any adhesive compound is not required for the connectionbetween the sensor heads 22 and the supporting plate 20. Thus, thelocating connector enhances the productivity and repairability of theoptical sensor array, and the manufacturer can reduce the productioncost of the keyboard musical instrument.

Although the particular embodiment of the present invention has beenshown and described, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the spirit and scope of the present invention.

More than one projection 42 may be formed on the supporting plate 20′ asshown in FIG. 16. In this instance, when the projection 41 is receivedin the locating hole 34, all the projections 42 are engaged with theguide groove 35, and prevent the sensor head 22 from the rotation aboutthe projection 41.

The projections 41 and 42 may be integrated into land portions 410 asshown in FIG. 17. The land portion is constricted so that the tips χ areengaged with the constricted portion. While the assembling worker slidesthe sensor head 22 on the upper surface 40 a, the land portion 410 ismoved into the guide groove 35. The land portion 410 passes over thetips χ. The tips χ are resiliently deformed so as to permit the leadingend portion is snugly received in the locating hole 34.

The projections 42 may be replaced with pairs of projections 420 asshown in FIG. 18. The projections 420 of each pair are located on bothsides of the sensor head 22. When the projection 41 is snugly receivedin the locating hole 34, the sensor head 22 is sandwiched between theprojections 42. Thus, the projections 420 prohibit the sensor head 22from the rotation about the projection 41.

Each of the slits 21 may be divided into three narrow slits 21A and 21Bas shown in FIG. 19. The center slit 21A is assigned to the sectorialplate 13, and the narrow slits 21B on both sides of the slit 21A areassigned to the resiliently deformable arms 33. This feature isdesirable, because the inner space is kept dark. When a worker assemblesthe sensor head 22 with the supporting plate 20″″, the worker firstlyinserts the resiliently deformable arms 33 into the narrow slits 21B,and brings the reverse surface of the sensor head 22 into contact withthe upper surface 40 a. Subsequently, the worker slides the sensor head22 on the upper surface 40 a. Then, the expander 40 b widens the gapbetween the resiliently deformable arms 33 so that the sensor heads 22reaches the coupler 40 c. The projection 41 is snugly received in thelocating hole 34, and the other projection 42 is engaged with the guidegroove 35 as similar to the above-described embodiment.

The present invention may be applied to the sensor head shown in FIG. 1.FIG. 20 shows a sensor head 50 according to the present invention. Thesensor head 50 has a light inlet port 50 a and a light outlet port 50 b,and two optical fibers 51 and 52 are inserted into the sensor head 50. Apair of pits 32 is formed in the sensor head 50, and the optical fibers51/52 are terminated at the receiving holes exposed to the pits 32.Adhesive compound are solidified in the pits 32 so as to fix the opticalfibers 51/52 to the sensor head 50. A pair of resiliently deformablearms 33 downwardly project from both sides of the sensor head 50, andhave the pawls 33 a as similar to the sensor head 22. The sensor heads50 are arranged on the supporting plate 20, and are connected to andlocated at proper positions on the supporting plate 20 by means of thelocating connectors of the sensor heads 50.

A shutter plate 61 may be attached to the hammer shank 5 b. In otherwords, the sectorial plate 13 with the gray code is replaceable with theshutter plate 61. The shutter plate 61 gradually intersects the lightbeam so that the hammer position is converted to the amount of lightincident on the light inlet port of the sensor head 22/50. The shutterplates 61 serves as plural light modifiers.

The optical sensor array according to the present invention may beincorporated in another sort of keyboard musical instrument. Anautomatic player piano is another sort of composite keyboard musicalinstrument. The automatic player piano is a combination of an acousticpiano and an automatic playing system. The acoustic piano is eithergrand or upright. The automatic playing system includessolenoid-operated key actuators installed under the keyboard and acontroller. When a set of music data codes is supplied to thecontroller, the controller analyzes the set of music data codes. Thecontroller specifies the keys to be moved, and determines times at whichthe keys start the motion. When the time comes, the controller suppliesa driving signal to the solenoid-operated key actuator under the key tobe moved. The solenoid-operated key actuator moves the key at thepredetermined time, and the key actuates the action unit so as to giverise to free rotation of the hammer toward the string. The automaticplayer piano may further have the hammer stopper.

The keyboard for practical use is yet another sort of the compositekeyboard musical instrument. The hammer assemblies and strings arereplaced with beaters and an impact absorber. While a trainee isfingering a piece of music on the keyboard, the depressed keys actuatethe associated action units, which in turn give rise to free rotation ofthe hammers through the escape. The beaters rebound on the impactabsorber, and the piano tones are not generated. The electronic tonegenerating system is incorporated in the keyboard for practical use. Inthis instance, the optical sensor array monitors the beaters, andperiodically report the current positions of the beaters to the dataprocessing unit. The data processing unit analyzes the series ofpositional data information, and produces the music data codes. Themusic data codes are supplied to the tone generator so as to generatethe electronic tones. Thus, the trainee checks the electronic tones forhis or her fingering.

A keyboard musical instrument may have keys greater than or less than88.

The projections 42 may be formed in a frustum of pyramid or anotherconfiguration.

In the above-described embodiment and modifications, the locating hole34 and guide groove 35 are formed in the sensor head, and theprojections 41/42 are formed on the supporting plate 20. However, theyare exchangeable. The locating hole and guide groove may be formed inthe supporting plate, and the projections 41/42 or land portion 410 maybe formed on the reverse surface of the sensor head.

The optical sensor array 10 according to the present invention may beused for monitoring plural moving objects such as, for example, pistons,links, keys of another use and so forth.

What is claimed is:
 1. An optical sensor array for converting currentpositions of moving objects to signals, comprising: a supporting platehaving plural retaining portions at intervals; plural sensor headsrespectively assigned to said plural retaining portions, andestablishing optical paths for light beams across said intervals; acombined optical device optically connected to said plural sensor heads,and selectively supplying light to and receiving said light from saidplural sensor heads through said optical paths; plural light modifiersconnected to said moving objects, and moved in said optical paths formodifying said light beams depending upon the current positions of theassociated moving objects; and plural locating connectors formedpartially in said plural sensor heads and partially in said pluralretaining portions, and connecting said plural sensor heads to targetpositions on said retaining portions through sliding motion of saidsensor heads on the associated retaining portions.
 2. The optical sensorarray as set forth in claim 1, in which said supporting plate is formedwith plural slits in said intervals so that said light beams extendacross said slits, and said plural light modifiers pass through theassociated slits for intersecting said light beams.
 3. The opticalsensor array as set forth in claim 2, in which said plural lightmodifiers are formed by plates where a gray code is formed for modifyingthe amount of light beams.
 4. The optical sensor array as set forth inclaim 2, in which said plural light modifiers are formed by shutterplates for modifying the amount of light means.
 5. The optical sensorarray as set forth in claim 2, in which said plural slits define saidretaining portions in said supporting plate in such a manner that eachof said retaining portions has a guide portion where an associated oneof said sensor heads slides, a part of a coupler contiguous to saidguide portion and a part of a locator, and each of said sensor heads isformed with another part of said coupler fixed to said part of saidcoupler for fixing the sensor head to the associated one of saidretaining portions and another part of said locator engaged with saidpart of said locator for keeping said sensor head at the targetposition.
 6. The optical sensor array as set forth in claim 5, in whichsaid part of said coupler includes an expander gradually increased froma first width equal to that of said guide portion to a second width anda grip portion having a third width wider than said first width andnarrower than said second width, and said another part of said couplerincludes resiliently deformable arms spaced from each other by adistance not wider than said third width so that said grip portion ispinched between said resiliently deformable arms at the end of saidsliding motion from said guide portion through said expander to saidgrip portion.
 7. The optical sensor array as set forth in claim 6, inwhich said resiliently deformable arms project from both side portionsof said each of said plural sensor heads, and said another part of saidcoupler further includes pawls inwardly projecting from leading ends ofsaid resiliently deformable arms so that said grip portion is furthersandwiched between said pawls and a surface of said each of said pluralsensor heads.
 8. The optical sensor array as set forth in claim 6, inwhich said pawls and said resiliently deformable arms are integral withsaid each of said plural sensor heads.
 9. The optical sensor array asset forth in claim 6, in which said resiliently deformable arms aremoved in two of said slits on both sides of said each of said retainingportions during said sliding motion of said each of said plural sensorheads from said guide portion through said expander to said gripportion.
 10. The optical sensor array as set forth in claim 9, in whicheach of said slits is divided into three sub-slits, and associated oneof said plural light modifiers and said resiliently deformable arms areassigned to one of said three sub-slits at the center position andremaining two sub-slits on both sides of said one of said threesub-slits.
 11. The optical sensor array as set forth in claim 5, inwhich said part of said locator includes a first projection formed onsaid each of said plural retaining portions and a second projectionformed on said each of said plural retaining portions, as wide as saidfirst projection and spaced from said first projection in the directionof said sliding motion, and said another part of said locator includes aguide groove as wide as said first and second projections, open at anend surface of said associated one of said plural sensor heads andextending in said direction of said sliding motion and a locating holeas wide as said first projection and merged with said guide groove atthe other end opposite to the end open at said end surface so that saidfirst projection and said second projection are received in saidlocating hole and said guide groove when said each of said plural sensorheads reaches said target position.
 12. The optical sensor array as setforth in claim 11, in which said each of said retaining portions andsaid each of said plural sensor heads have a first centerline extendingin said direction of said sliding motion and a second centerline,respectively, and said first and second projections and both of saidguide groove and said locating hole are formed on said first centerlineand said second centerline, respectively.
 13. The optical sensor arrayas set forth in claim 11, in which said another part of said locatorfurther includes at least one third projection spaced from said secondprojection in said direction of said sliding motion and received in saidguide groove together with said second projection when said each of saidplural sensor heads reaches said target position.
 14. The optical sensorhead as set forth in claim 11, in which said first projection is mergedwith said second projection so as to form a land portion as wide as saidguide groove and said locating hole and extending in said direction ofsaid sliding motion.
 15. The optical sensor array as set forth in claim5, in which said part of said locator includes a first projection formedon said each of said plural retaining portions and at least two secondprojections formed on said each of said plural retaining portions andspaced from each other in a direction perpendicular to the direction ofsaid sliding motion by a distance equal to a width of said each of saidplural sensor heads, and said another part of said locator includes aguide groove as wide as said first projection, open at an end surface ofsaid associated one of said plural sensor heads and extending in saiddirection of said sliding motion and a locating hole as wide as saidfirst projection and merged with said guide groove at the other endopposite to the end open at said end surface so that said at least twosecond projections prevent said each of said plural sensor heads aboutsaid first projection received in said locating hole when said each ofsaid plural sensor heads reaches said target position.
 16. A keyboardmusical instrument for generating audible tones from an electric signal,comprising: plural tone specifying mechanisms selectively actuated by aplayer for specifying tones to be generated; a tone generating unitgenerating the tones specified by said player through said plural tonespecifying mechanisms; and an optical sensor array monitoring saidplural tone specifying mechanisms so as to determine the tone specifyingmechanisms actuated by said player, and including a supporting platehaving plural retaining portions at intervals, plural sensor headsrespectively assigned to said plural retaining portions and establishingoptical paths for light beams across said intervals, a combined opticaldevice optically connected to said plural sensor heads and selectivelyto supplying light to and receiving said light from said plural sensorheads through said optical paths, plural light modifiers connected tosaid plural tone specifying mechanisms, and moved in said optical pathsfor modifying said light beams depending upon the current positions ofthe associated tone specifying mechanisms, and plural locatingconnectors formed partially in said plural sensor heads and partially insaid plural retaining portions and connecting said plural sensor headsto target positions on said retaining portions through sliding motion ofsaid sensor heads on the associated retaining portions.
 17. The keyboardmusical instrument as set forth in claim 16, in which said supportingplate is formed with plural slits in said intervals so that said lightbeams extend across said slits, and said plural light modifiers passthrough the associated slits for intersecting said light beams.
 18. Thekeyboard musical instrument as set forth in claim 17, in which saidplural slits define said retaining portions in said supporting plate insuch a manner that each of said retaining portions has a guide portionwhere an associated one of said sensor heads slides, a part of a couplercontiguous to said guide portion and a part of a locator, and each ofsaid sensor heads is formed with another part of said coupler fixed tosaid part of said coupler for fixing the sensor head to the associatedone of said retaining portions and another part of said locator engagedwith said part of said locator for keeping said sensor head at thetarget position.
 19. The keyboard musical instrument as set forth inclaim 18, in which said part of said coupler includes an expandergradually increased from a first width equal to that of said guideportion to a second width and a grip portion having a third width widerthan said first width and narrower than said second width, and saidanother part of said coupler includes resiliently deformable arms spacedfrom each other by a distance not wider than said third width so thatsaid grip portion is pinched between said resiliently deformable arms atthe end of said sliding motion from said guide portion through saidexpander to said grip portion.
 20. The keyboard musical instrument asset forth in claim 19, in which said resiliently deformable arms projectfrom both side portions of said each of said plural sensor heads, andsaid another part of said coupler further includes pawls inwardlyprojecting from leading ends of said resiliently deformable arms so thatsaid grip portion is further sandwiched between said pawls and a surfaceof said each of said plural sensor heads.
 21. The keyboard musicalinstrument as set forth in claim 20, further comprising plural vibratorystrings associated with said plural tone specifying mechanisms andselectively struck with hammers of said plural tone specifyingmechanisms for generating acoustic tones.
 22. The keyboard musicalinstrument as set forth in claim 21, in which said hammers are monitoredby said optical sensor array so that said plural light modifiers areconnected to said hammers, respectively.
 23. The keyboard musicalinstrument as set forth in claim 21, further comprising a hammer stopperchanged between a blocking position provided on trajectories of saidhammers and a free position provided out of said trajectories, and saidhammers rebound on said hammer stopper at said blocking position beforestriking said strings.
 24. The keyboard musical instrument as set forthin claim 23, in which said hammers are monitored by said optical sensorarray so that said plural light modifiers are connected to said hammers,respectively.